Last Updated:
June 05, 2000

 Research Interests

  • Fabrication Processes for Next-Generation Magnetic Storage Devices (This is funded by the Multi-Disciplinary University Research Initiative, monitored by Maj. H.C. DeLong of the Air Force Office of Scientific Research, and funded by Department of Defense, and also subcontracts from DARPA/ONR through Honeywell and Florida State University.). Some of the key developments to date:
    • invention of new high-rate etching process for NiFe and NiFeCo thin films, using either ECR or ICP Cl2/Ar plasmas to balance formation of chloride etch products, and their subsequent removal by ion-assisted desorption. Special attention is being paid to avoidance of post-etch corrosion through both in-situ plasma cleaning and ex-situ wet chemical cleaning (K.B. Jung).
    • study of alternative, non-chlorinated etch chemistries for magnetic thin films. Novel plasma chemistries which avoid the need for post-etch cleaning are being investigated (K.B. Jung).
    • development of wet and dry patterning processes for the Heusler alloy system NiMnSb. We have found that fluorine-based chemistries (SF6, NF3) produce extremely high etch rates for NiMnSb, and can also be used to etch the Al2O3 insulating layers needed in GMR spin valve structures (J. Hong).
    • development of ultra high resolution pattern transfer processes for LaCaMnO3 and SmCo films for use in CMR structures. Cl2/Ar chemistries are found to etch SmCo at ~7,000Å·min-1, but Ar+ milling produces the fastest rates for LaCaMnO3 (J.J. Wang). Most of these projects are joint with Prof. Childress’s group.
  • Processing of Wide Bandgap Semiconductor Materials – GaN, SiC and Related Compounds (This is funded by DARPA/EPRI (E.R. Brown/J. Melcher) by NSF (L.D. Hess) and by Sandia National Laboratories). Some of the current projects:
    • ultra high temperature rapid thermal annealing for implant activation in GaN and SiC. Activation efficiencies >90% have been achieved in Si-implanted (5x1015cm-2, 100keV) GaN after AlN-capped annealing at 1400OC, with DSi £10-13cm2·s-1 (X. Cao).
    • properties of C, O and H in GaN and related materials. Carbon is found to be an inefficient acceptor in as-grown GaN, and may contribute to the residual n-type conductivity in In-containing nitrides where it should be a donor. Implanted C causes compensation in n-type GaN.. Oxygen creates a shallow donor in GaN (30meV), with low diffusivity. Hydrogen is found to passivate all acceptor dopants in GaN (Be, C, Ca, Mg, Cd) and to readily enter the material at temperatures of £100OC (J.W.Lee).
    • wet and dry etching processes for GaN. Both ECR and ICP reactors have been shown to produce much higher etch rates for the nitrides relative to conventional RIE. The fastest etch rate ever reported for GaN, was obtained with a novel chemistry, ICl/Ar. Photoelectrochemical etching using UV illumination of KOH solutions is being investigated (H. Cho, postdoctoral research associate; T. Maeda, visiting scientist from Fujitsu, Japan).
    • high rate, low-damage etching of SiC and SiCN using ICP NF3 plasmas, Excellent rates (3,500Å·min-1) at low biases (£100V) have been achieved, with outstanding etch anisotropy and surface quality (J.J. Wang).
    • stability of W-based ohmic contacts on nitrides (Joint with F. Ren (Bell Laboratories), J.C. Zolper (ONR), M. Eizenberg (Technion) and M.W. Cole (ARL). This project studies metallurgical reactions and electrical properties of W and WSiX contacts on InGaN of different In content, i.e. bandgap (joint with Prof. Abernathy’s group).
  • Fabrication modules for Novel Electronic Materials (funded by Plasma Therm). Some current projects:
    • selective and non-selective wet and dry etching of the GaAs/AlGaAs and GaAs/InGaP heterostructures for high speed devices (D. Hays, undergraduate).
    • high rate dry etching of III-V semiconductors. Etch rates above 1mm·min-1 achieved for InP and related materials in Cl2/Ar, ICl, IBr and other novel plasma chemistries (J.W. Lee and J. Hong).
    • etching of flat panel electroluminescent display materials (J.W. Lee, joint with Prof. Holloway’s group).